Why Objects.hash() returns different values for the same input?

Question

I ran the follow script(java), and it gave me the weird result. Does anyone can help to explain?

import java.util.Objects;
import org.apache.log4j.Logger;

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Answer 1

It's because hashCode for int[] is not overridden. There is no reason why two instances of int[] should have the same hashCode, even if the entries are the same.

Try this:

System.out.println(new int[] {1, 2}.hashCode());
System.out.println(new int[] {1, 2}.hashCode());

You will almost certainly see two different integers.

A good way to use Objects.hash with arrays is to pass Arrays.hashCode(array) instead of the actual array. In your case you could do:

Objects.hash("getDemoCache", "1", Arrays.hashCode(new int[]{1, 2}))